1. Field of the Invention
The present invention concerns a system for simultaneously controlling Heat expansion and thermal stress in a gas turbine disk.
2. Description of the Prior Art
Various processes for the thermal conditioning of gas turbine disks are already known. French Patent No. 1593039, filed Sept. 27, 1968 by Societe Anonyme Bennes Marrel, describes a system for cooling a gas turbine. Cold air from a compressor is directed toward the rim of the disk through an appropriate conduit opening into a seal facing said rim. Hot air is -bled from the location of the nozzle associatedwith the disk. Part of the hot air is sent directly over the outer part of the disk's rim, with the rest being mixed with the cold air emerging from the above-mentioned seal. Cold air bled from the compressor is channeled into an annular chamber situated between the opposing surfaces of two turbine disks. The inner circumferential wall of this chamber includes perforations leading into two other annular chambers separated by an essentially radial partition, so that cold air escaping from said annular chambers will sweep the two opposing surfaces of the disk. The other surface of the second disk is itself swept by a flow of air resulting from the mixture of atmospheric air with air which has circulated around the exhaust pipe. All of these arrangements use hot and/or cold air, mixed or unmixed, from various sources, to thermally condition the rim of one or more gas turbine disks. The system described above obviously does not permit systematic conditioning of the temperature of each disk of the gas turbine, particularly at preset moments in its operating cycle.
French Patent No. 2,290,574, filed Nov. 5, 1974, describes a group of gas turbines comprising, on either side of a disk, two perforated plates behind which is directed a mixture of two flows of air, hot and cold, arriving from separate channels. The air mixtures emerging from said metal plates flow over the opposite surfaces of the disk near the rim.
The French Patent Nos. 2,280,791 and 2,467,292 to the same Assignee describe a system for automatically regulating the clearance between the rotor blades of a gas turbine and the opposing wall of its stator. This adjustment is achieved by directing jets of appropriately temperature-adjusted heating or cooling air over the outer surface of the stator wall. These jets of thermal conditioning air do not come into contact with the rotor blades or the rotor disk.
Among the various known processes for the thermal conditioning of gas turbine disks, the most effective is certainly the process in which at least one of the two surfaces of the disk is jets of air, as described in the article published by Metgzer and Grochowsky in the Journal of Heat Transfer (vol. 99, Nov. 1977, pp 663-667).